During the past several years, the popularity and viability of fuel cells for producing large and small amounts of electricity has increased significantly. Fuel cells conduct an electrochemical reaction with chemicals such as hydrogen and oxygen to produce electricity and heat. Fuel cells are similar to batteries but fuel cells can be “recharged” while providing power. Fuel cells are also much cooler and cleaner than devices that burn hydrocarbons.
Fuel cells provide a DC (direct current) voltage that may be used to power motors, lights, computers, or any number of electrical appliances. There are several different types of fuel cells, each using a different chemistry. Fuel cells are usually classified by the type of electrolyte used. Fuel cell types are generally categorized into one of five groups: proton exchange membrane (PEM) fuel cells, alkaline fuel cells (AFC), phosphoric-acid fuel cells (PAFC), solid oxide fuel cells (SOFC), and molten carbonate fuel cells (MCFC).
Each of the fuel cells mentioned above uses oxygen and hydrogen to produce electricity. Ambient air typically supplies the oxygen for a fuel cell. In fact, for the PEM fuel cell, ordinary air may be pumped directly into the cathode. However, hydrogen is not as readily available as oxygen. Hydrogen is difficult to generate, store, and distribute for a number of reasons including posing a potential safety hazard. Consequently, strict safety precautions are taken in order to reduce potential safety hazards.
It can be undesirable to store large amounts of gaseous fuel (such as hydrogen) in a fuel cartridge because such storage can raise safety concerns and provide less than optimal energy density. Moreover, in those instances where fuel-containing substances are stored in a fuel cartridge, conventional devices for causing the gaseous fuel to be released do not provide precise control over the process. This lack of control can lead to the release of more fuel than is required by the fuel cell raising a number of safety concerns.